The publication of JP-A No. 09-032984 (the drawings, especially FIGS. 14 to 17) filed by the present applicant already discloses a fluid coupling comprising a first and a second coupling member having respective fluid channels communicating with each other, a gasket in the form of an apertured disk and interposed between abutting end faces of the two coupling members and screw means for fastening the two coupling members together. Each of the first and second coupling members is provided in the abutting end face thereof with an annular projection for holding the gasket. The publication also discloses a first and a second coupling member each provided with an annular recessed portion formed in an abutting end face thereof and having a flat bottom face. The recessed portions of the two coupling members define a space having an annular gasket disposed therein. The gasket has an annular ridge formed on each of opposite side surfaces thereof.
With the fluid coupling described above, the end face of each coupling member including the gasket holding annular projection requires high-precision working including provision of a mirror finish, necessitates time and labor for working and therefore has the problem that the working offers an obstacle to an improvement in the efficiency of the entire process for manufacturing the coupling. Accordingly, it appears preferable to use couplings of the type wherein the gasket has annular ridges on the respective opposite side surfaces, whereas a detailed study still remains to be made about the shape of gaskets, and no microscopic studies have heretofore been made especially about the shape of the projections or ridges to be provided on the gasket although ridges of various shapes may be usable.
An object of the present invention is to construct a proper seal structure between the coupling members with attention directed also to the shape of the gasket and to provide a fluid coupling which is improved in both sealing properties and durability and a method of designing the coupling.